Fiber-spinning compositions



Patenteci Nov. 24-, 1953 UNITE-D S TATES PAT T 0F Fl C E FIBER-:SPJNNING COMPOSITIONS 'GeorgefE. Ham, Dayton, Ohio, assignor, .by mesneassignments, to 'The Chemstrand Corporation, a corporation of Delaware.No Drawing. Application'May 24, 1951, Serial No.-228,129

solvent and thereafter extruding the composition through .a die or.spinneret, into a medium which removes the solvent and precipitates.the polymer in continuous form. Although many solvents for.polyacrylonitrile are known and described in the literature, most ofthem are costly,

difficult to prepare, and sensitive to the presence of non-solvents,such as water.

The primary purpose of this invention is to provide a new andinexpensive solvent for polyacrylonitrile and copo'lymershaving85 ormore per cent by weight of acrylonitrile. A [further purpose of thisinvention is to provide anew procedure for preparing synthetic .fibers.from acrylonitrile. .A still further purpose of this invention is toprovide .a .means. for using vhaloacetonitrile, normally a non-solventas a medium for spinning acrylonitrile .fibers.

It has been discovered that, although neither the haloacetonitrile norwater is a solvent for acrylonitrile polymers, amixture of the two is avery effective solvent. "This .is an unusual phenomenon becausegenerally the presence of nonsolvents, and water in particular, impedes.any solvent action which the principal medium may have; for example,dimethylformamide Wellknown as an excellent solvent for acrylonitrilepolymers becomes a non-solvent if it contains as little as fivepercentof "water. Also asolution of acrylonitrile polymer in dimethylformamidewill be precipitated by the addition of very small amounts of Water orother non-solvents. 'In the practice of this invention it "has beenfound that mixtures of "from 99 per cent 13070 per cent ofthe'haloacetonitr'i'le and from one per cent to 30 per cent of water areexcellent solvents for the acrylonitril'e polymers.

It has been found that "the suitable haloacetonitriles are thehalogenated'acetonitriles and especiallytho'se of chlorine, fluorine,and bromine.

From one to three halogens, either the same or 2 different, may bepresent in the :haloacetonitrile. The generic class of usefulacetonitriles may-be represented by the structural formula:

X X CCN XII whereinX, X, and each maybe hydrogen or halogen, providedthat at least one of the X, .X', and X is a halogen atom. Typicalha'loaceton-itriles are chloroacetonitrile, =fluoroacetonitrile,bromoacetonitr-ile, dichloroacetonit-rile, trichloroacetoni-trile,:trifiuoroacetonitrile, and -=chlorofiuoroaeetonitrile.

It has been found that polymers and copolymers of acrylonitrileusetul'in the practicerof this invention are those which are prepared bythe polymerization of an olefinic monomeric substance of which at least?85 per cent of the total polymerizable monomers is a'crylonitri le.These may be copolymers of '85 or more percent of acrylonitrile and'upto 15 per cent 'of other monomers copolymerizable therewith, for examplevinyl acetate, vinylidene chloride, vinyl chloride,

z-dialkyl fumarates, in which the alkyl radical has up to four carbonatoms, the dialkyl maleates in which the alkyl radical has up to fourcarbon atoms, the alkyl *rnethacrylates and acrylates, wherein the alkylradical has up to four carbon atoms, styrene, vinylpyr-idine and thealkyl substituted vinylpyridi-nes, N-viny-lim'idazole, and

other vinylzsubstituted heterocyclic nitrogen compounds, allylchloroac'eta-te, methallyl chloroacetate, allyl ,g-lycidyl-ether,-methallyl glycidyl ether, and other zmonoeolefinic compositionspolymerizable with .acrylonitrile, Of particular utility are thecopolymers of acrylon-itrile and olefinic monomers which contain adye-receptive Nheterocyclic nucleus orwhich contains a chloroacetate,chloroacrylate, a {s-chloroethyl or other active halogen containingnucleus, glycidyl radical or other groups capable of being convertedinto a dye-receptive group by subsequent chemical reaction, for example,a tertiary-amine, a thiourea or a Z-mercaptobenzothiazole derivative.

Another useful type of acrylcnitrile polymer is that wherein thepolyacrylonitrile or a copolymer of acrylonitrile and minor proportionsof another polymerizable monomer is blended with a polymer of .a monomercontaining a dye-receptive 'N-heterocyclic nucleus, 01' otherdye-receptive nucleus, or a nucleus such as chloroacetate or otheractive chlorine containing radical, a glycidyl radical or other radicalwhich can be converted into dye-receptive form by Subsequent chemicalreaction. The blended polymers will be comprised principally ofacrylonitrile in poly mcric form and sufiicient of the dye-receptiveradical, two to fifteen per cent of the total monomer, to enable thefinal blended composition to be receptive of dyestuff and adaptable toconventional dyeing procedures.

The spinning solutions are prepared from mixtures of haloacetonitrilcand water by dispersing the finely divided acrylonitrile polymer orblended polymers with the solvent mixture and heating until a uniform,homogeneous mixture is obtained. In general, the solutions will containfrom five to 35 per cent of polymer and the balance of the solventmixture of a haloacetonitrile and water.

In the practice of this invention, as in the preparation of allacrylonitrile fibers, the molecular weight of the copolymer is ofsubstantial importance. The copolymer should have a molecular weight inexcess of 10,000, and preferably in excess of 25,000. These molecularweights are determined by measuring the viscosity in suitable solventsin the manner well-known to the art. It is also very desirable to usecopolymers which are substantially uniform throughout, especially withrespect to composition and molecular weight. These uniform copolymersenable the practice of the invention more economically by permitting theutilization of continuous uninterrupted spinning through theminimization of fiber fractures and clogging of the spinneret.

In the practice of this invention the polyacrylonitrile and copolymersof acrylonitrile are preferably used in finely divided form. Althoughmass polymers may be ground to desirable size and so used, emulsion orsuspension polymers are preferably employed in the preparation of thespinning solutions, and the sub-divided state in which the polymer isobtained from the emulsion is used directly. The polymer is mixed withthe solvent mixture and stirred until a uniform solution is formed. Insome cases heating may be necessary or desirable to expedite thesolution preparation. Since water is a critical component of the solventmixture, the polymer, as obtained from the preferred aqueous dispersionpolymerizations, need not be dried or even separated from the watermedium. The polymer containing a substantial proportion of water may bemixed with the haloacetonitrile and the solution effected withoutaddition of more water. It may in some circumstances be necessary toremove part of the water present, so as to utilize the optimumproportions of water and haloacetonitrile. It is often advantageous towash the polymer with water to remove traces of polymerization reagents,monomers and other impurities, and to blend the wet polymer, recoveredby decantation or filtration, with haloacetonitrile and sufficient waterto produce the optimum solvent proportions. The solution preparation maybe conducted in any conventional mixing machine, for example a doughmixer.

In the spinning of fibers from acrylontrile solutions in a mixture ofWater and haloacetonitrile, it is desirable to use a solution of as higha concentration of polymer as possible, but the maximum concentration isdependent upon the molecular weight of the polymer and the visocitycharacteristics of the polymer-solvent mixture. To obtain fibers ofoptimum physical properties, polymers of molecular weights in excess of25,000 are used, and with such polymers it is only possible to dissolvea relatively small proportion in the haloacetonitrilc-water mixtureswithout achieving an impracticably high viscosity. Although. as littleas five per cent solutions of the polymer can be used in the spinningoperation, such low concentrations are undesirable because theynecessitate the removal and the recovery of too much solvent from themedium into which the fiber is extruded. Dilute spinning solutions alsotend to make the resultant fibers more bulky by reason of the excessivequantity of solvent removed from the inside of the fiber. Dilute polymersolutions also reduce the spinning speeds by lengthening the period oftime required for coagulation of the fiber and complete removal of theresidual solvent which is usually objectionable. The concentration ofpolymer in the spinning solution is generally between ten and twenty percent for polymers of optimum molecular weight. Lower molecular weightpolymers may be spun in solutions of as high as 35 per cent. Theconcentration of the polymer will ultimately be determined byconsidering the desired physical properties of the fiber and the desiredspinning speed, the latter being a function of the concentration and.the viscosity of the spinning solution. The viscosity will often dependupon the chemical composition and the molecular weight of the polymer.The optimum concentration can best be determined by selecting a uniformhigh molecular weight polymer having good fiberforming properties, anddissolving it in as little of the haloacetonitrile-water mixture as ispossible to form a viscous solution capable of being spun at convenienttemperatures.

The spinning solution may be modified by the addition of other materialsfor the development of special properties in the resulant fiber. Forexample, finely divided titanium dioxide, or other white pigment, can beadded to the spinning solution in order to reduce the lustre of thefibers prepared therefrom. Similarly, other resins may be added withoutimpairing the homogeneity of the ccpolymer solution. For example, smallamounts of thermoplastic resins improve the spinnability of the solutionand the dyestuff affinity of the fiber. Thermosetting resins in theuncured state may also be added, and the resultant fibers subsequentlycured to improve the fiber strength and elasticity. Proteins also may beadded for the purpose of increasing dyestuff affinity, although slightreductions in water resistance are simultaneously developed. Additionsof cellulose derivatives may also be made for developing stiffness anddyestufi affinity in the resulting fibers.

The fibers are spun by extruding the polymer solution through an orificeor a spinneret having a plurality of orifices into a medium whichremoves the haloacetonitrile and water. The volume rate of passage ofthe solution through the spinneret must be constant in order to producea fiber of uniform size. This is best achieved by using a positivelydriven gear pump to deliver a constant fiow of solution regardless ofminor changes in viscosity and the variable resistance offered by thespinneret. It is also desirable to pass the solution, which has beenfiltered, into one or more additional filters before the spinneret toremove the last traces of foreign matter and particlcs of incompletelydissolved polymer. The polymers may be delivered to the gear pump bypressure applied by an inert gas to the solution reservoir, which isheated if necessary to make the solution fluid enough to pass throughthe conduits. The extruding operation may be operated :a'televatedtemperatures, but .at temperatures not in excess :of the boiling pointof the haloacetonitrile waiter mixture.

The medium into which the solution is extruded and which removes thesolvent may be either liquid or gaseous. The method involving the use ofliquids, known as wet spinning, utilizes aqueous mediums, alcohol,glycerol, methyl :ethyl 'ketone, 'or other liquids in whichthehaloacetonitrile is at least in part soluble, but in which the copolymeris insoluble. The solutions of acrylonitrile polymers inhaloacetonitrile and water mixtures are unusually adapted to dryspinning techniques in which the solution is extruded into a gaseousatmosphere at relatively high temperatures, so that the haloacetonitrileand water are evaporated from the surface of the fiber and removed inthe gas stream to suitable recovery apparatus. Suitable gases are air,nitrogen, oxygen, carbon dioxide, and methane. The dry spinning methodgenerally is operative at higher temperatures, but the maximumtemperature to which the fiber can be subjected is about the boilingpoint of the haloacetonitrile and water mixture, since evaporationwithin the fiber may cause bubbles in the fiber structure. The fiber maybe heated by convection from the gaseous medium or by radiation from thewalls of the confining vessel. Generally a combination of bothconvection and radiation is involved.

-readily adaptable to spinning acrylonitrile polymer solutions inhaloacetonitrile-water mixtures. Similarly, conventional automaticmachinery for continuous spinning, drying the thread if necessary, andwinding it upon suitable spools, can be used. As in the case of mostsynthetic fibers, those obtained by spinning haloacetonitrile-watersolutions of acrylonitrile polymers must be oriented by stretching inorder to develop the optimum physical properties. If desired part of thestretching may be accomplished in the spinning medium. by drawing thefiber from the medium at a rate greater than the rate of extrusion. Bothcontinuous and staple fibers may be produced from the describedhaloacetonitrile-water solutions. Oriented staple fibers may be made bystretching the continuous fiber and then cutting to the desired lengthsfor use in conventional textile fiber processes, either alone or inadmixture with other natural or synthetic fibers. The solutions ofacrylonitrile polymers in haloacetonitrile-water mixtures are alsouseful for the preparation of films by casting the solutions on smoothsurfaces and evaporating the haloacetonitrile and water. The solutionsare also useful as coating compositions.

Further details of the invention are set forth with respect to thefollowing specific examples:

Example 1 Two parts by weight of an emulsion copolymer of 97 per cent ofacrylonitrile and three per cent of vinyl acetate were dispersed in tenparts of chloroacetonitrile and ten parts of water. The resultingmixture was heated with stirring for minutes at 80 C. whereby ahomogeneous copolymer solution was obtained. A second supernatant liquidphase was comprised essen tially of eight parts of water. Fibers andfilms were prepared both by precipitation of the polymer: solution withalcoholxand :by evaporation of :the solvent. .A similar experiment wasattempted usingchloroacetonitrile without :water but no solution wasobtained.

Example 2 A homogeneous copolymer solution was prepared by heating withstirring at C.

What I claim is:

1. A new composition of matter comprising a homogeneous, misciblemixture of a polymer of a monomeric mixture of which acrylonitrile is atleast per cent by weight of the total monomer content, homogeneouslydispersed to the extent of from five to 35 per cent in a mixture of from70 to 99 per cent of chloroacetonitrile and from one to 30 per cent ofwater.

2. A fiber-spinning composition comprising a homogeneous, misciblemixture of a polymer of a monomeric substance of which acrylonitrile isat least 85 per cent by weight of the total polymerized monomers and asolvent medium comprised of from one to 30 per cent of water and from 70per cent to 99 per cent of chloroacetonitrile.

3. The composition defined by claim 1 wherein the polymer ispolyacrylonitrile.

4. The composition defined by claim 1 wherein the polymer is a copolymerof from 85 per cent to 98 per cent of acrylonitrile and from two to 15per cent of vinylpyridine.

5. The composition of claim 1 wherein the polymer is a copolymer of atleast 85 per cent of acrylonitrile and up to 15 per cent of vinylacetate.

6. The composition defined by claim 1 wherein the polymer is a blend ofa polymer of at least 85 per cent of acrylonitrile and a polymer of from30 per cent to '70 per cent of vinylpyridine.

7. The composition defined by claim 2 wherein the polymer ispolyacrylonitrile.

8. The composition defined by claim 2 wherein the polymer is a copolymerof from 85 per cent to 98 per cent of acrylonitrile and from two to 15per cent of vinylpyridine.

9. The composition defined by claim 2 wherein the polymer is a copolymerof at least 85 per cent of acrylonitrile and up to 15 per cent of vinylacetate.

10. The composition defined by claim 2 wherein the polymer is a blend ofa polymer of at least 85 per cent of acrylonitrile and a polymer of from30 per cent to 70 per cent of vinylpyridine.

11. A new composition of matter comprising a homogeneous, misciblemixture of a polymer of a monomeric mixture of which acrylonitrile is atleast 85 percent by weight of the total monomer content, homogeneouslydispersed to the extent of from 5 to 35 percent in a mixture comprisedof from one to 30 percent of water and from 70 to 99 percent ofhaloacetonitrile.

12. The composition defined by claim 11 wherein the polymer ispolyacrylonitrile.

13. The composition defined by claim 11 wherein the polymer is a.copolymer of from 85 to 98 percent of acrylonitrile and from two to 15percent of vinylpyridine.

14. The composition of claim 11 wherein the polymer is a copolymer of atleast 85 percent of acrylonitrile and up to 15 percent of vinyl acetate.

15. The composition defined by claim 11 wherein the polymer is a blendof a polymer of at least 85 perent of acrylonitrile and a polymer offrom 30 to 70 percent of vinylpyridine.

16. A fiber-spinning composition comprising a homogeneous, misciblemixture of a polymer of a monomeric substance of which acrylonitrile isat least 85 percent by weight of the total polymerized monomers and asolvent medium comprised of from one to 30 percent of water and from 70to 99 percent of haloacetonitrile.

GEORGE E. HAM.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,496,267 Chaney Feb. 7, 1950

1. A NEW COMPOSITION OF MATTER COMPRISING A HOMOGENEOUS, MISCIBLEMIXTURE OF A POLYMER OF A MONOMERIC MIXTURE OF WHICH ACRYLONITRILE IS ATLEAST 85 PER CENT BY WEIGHT OF THE TOTAL MONOMER CONTENT, HOMOGENEOUSLYDISPERSED TO THE EXTENT OF FROM FIVE TO 35 PER CENT IN A MIXTURE OF FROM70 TO 99 PER CENT OF CHLOROACETONITRILE AND FROM ONE TO 30 PER CENT OFWATER.